Re: [FFmpeg-devel] [PATCH] lavu/opt: Mention that AVOptions is not reentrant

[Andrew Sayers <ffmpeg-devel@pileofstuff.org>]

On Thu, Jun 06, 2024 at 01:17:48AM +0200, Michael Niedermayer wrote:
[...]
> AVOption simply provides light weight access to the struct fields.
> Calling AVOption non re-entrant in modifying a field you arent even allowed
> to modify from 2 threads is confusing

I think you're saying there's already a rule about modifying AVOptions from
2 threads.  Could you explain that in more detail?

> If you want to modify a field from 2 threads that field could be some sort
> of atomic type. This can then easily be added to AVOption

Doing that for a single option would involve publicly guaranteeing its
representation for at least one major version.  At that point, you might as well
just tell people to access it as a member of a public struct.

To be clear - this isn't a programming problem, it's a design problem.
The interface currently allows external developers to assume something will
always work when it's actually just something that could be supported some day.
Writing up the current behaviour as a guarantee lets them avoid writing code
that will generate hard-to-reproduce bugs, at the cost of making it slightly
harder for us to do something we've never needed to do in the past.
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